The busy London Underground may seem an unlikely location for heritage train operation, especially involving steam. However, this was the world's first Underground railway network, and the original sections were built to main line gauge using steam traction. London Transport and its successor London Underground Ltd have been acutely aware of the significance of this and have strived to preserve and present their heritage. Over the decades, open days and special trains operated over parts of the system. This included the running of steam-, diesel- and electric-hauled trains for the public to ride on, while at the same time maintaining the normal level of Underground train service on these lines. These special trains ran not only in the open-air outer sections of the network, but even on occasion through the cut-and-cover tunnel sections of central London. New signalling systems mean that this is unlikely to happen again, but the London Transport Museum continues to offer a programme of exhibitions, guided history tours and open days at the Acton museum depot. This book looks back at the principal events since 1963.